Forced convection oven

ABSTRACT

A gas fired forced convection oven comprises a heating or cooking zone, fan means for circulating a hot gaseous atmosphere in said zone, the gas distribution means including at least one fuel gas burner located in a passage leading to said zone, a throat located in the passage downstream of said burner and means for deflecting the circulating atmospheric gas issuing from said fan away from said burner and into said throat whereby the circulating atmospheric gas mixes with the combustion gases from the burner and enters the said heating or cooking zone.

United States Patent Inventor Donald Richard Borge London, England Appl.No. 7,684 Filed Feb. 2, 1970 Patented Dec. 14, 1971 Assignee The GasCouncil London, England Priority Jan. 31, 1969 Great Britain 5,403/69FORCED CONVECTION OVEN 3 Claims, 2 Drawing Figs.

US. Cl 126/21 A Int. Cl F24c 15/32 Field olSearch 126/19, 21, 21 A, 39C, 273

[56] References Cited UNlTED STATES PATENTS 2,524,272 10/1950 Sage126/21 A UX 2,817,506 12/1957 Albright 126/21 A UX 3,384,068 5/1968Perry et a1. 126/21 A 3,411,493 11/1968 Everson et a1. 126/21 A3,463,138 8/1969 Lotter et a1. 126/21 A Primary Examiner-Charles J.Myhre AnorneyLarson and Taylor ABSTRACT: A gas fired forced convectionoven comprises a heating or cooking zone, fan means for circulating ahot gaseous atmosphere in said zone, the gas distribution meansincluding at least one fuel gas burner located in a passage lead ing tosaid zone, a throat located in the passage downstream of said burner andmeans for deflecting the circulating atmospheric gas issuing from saidfan away from said burner and into said throat whereby the circulatingatmospheric gas mixes with the combustion gases from the burner andenters the said heating or cooking zone.

FORCED CONVECTION OVEN BACKGROUND OF THE INVENTION This inventionrelates to forced convection ovens and is particularly concerned withgas fired ovens of this type. Such ovens are conventionally used to heata number of separate containers or portions of precooked foods but theovens may also be used for normal cooking purposes if required. Adesirable characteristic of this form of oven is uniform heatingthroughout the oven space and such uniformity is obtained by controllingthe temperature, quantity and flow patterns of the circulating medium.

In the present forms of gas heated convection oven the circulatingmedium is generally air heated indirectly by some form of heatexchanging system, the combustion products from the gas burners beingvented to atmosphere. This arrangement tends towards operatinginefficiency and adds considerably to the manufacturing and runningcosts.

It is therefore an object of the present invention to provide animproved form of gas fired forced convection oven in which theaforementioned disadvantages are minimized.

SUMMARY OF THE INVENTION According to the invention a forced convectionoven comprises a heating or cooking zone, fan means for circulating ahot gaseous medium in said zone, the gaseous medium distribution meansincluding at least one fuel gas burner located in a passage leading tosaid zone, a pressure reducing throat located in the passage downstreamof said burner and means for deflecting the circulating gaseous mediumissuing from said fan away from said burner and into said throat wherebythe circulating medium mixes with the combustion gases from the burnerand enters the said heating or cooking zones.

in a preferred arrangement the circulating medium enters the heating orcooking zone through apertured side panels flowing substantiallyhorizontally across the cooking zone and leaves via an apertured rearpanel. The fan may be located in a compartment positioned below theheating or cooking zone.

To enable the nature of the invention to be more readily understood, oneembodiment of the invention will now be described, solely by way ofexample, with reference to the accompanying drawing, which showsdiagrammatically a preferred form of oven. In the drawing:

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a midsectional side view ofthe oven and FIG. 2 is a midsectional view looking from the front of theoven.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing aforced convection gas fired oven comprises a heating or cooking zone 1having perforated side plates 2 through which a hot gaseous mediumcomprising a mixture of air and combustion products from the fuelburners used to heat the oven, is supplied by means of a fan 3. The fanis located in a distribution chamber 4 positioned below the heating orcooking space and circulates the gaseous medium to the side plates via asupply duct 5 at each side of the oven.

The side plate apertures 6 are arranged and dimensioned to provide asubstantially uniform flow of gas across the heating or cooking zone andthe gas is withdrawn from the oven zone through an apertured back plate10 and returned to the distribution chamber and fan via an extract duct7. The fan is driven by an electric motor 8.

The oven is heated by fuel gas burners 9 positioned at each side of theappliance, the burner ports in each case being arranged to fire directlyupwards into a lower extension of the supply duct 5. A pressure reducingthroat I1 is fonned at the lower end of each duct 5 and deflector orbaffle plates 12, associated with the distribution chamber 4, arearranged to shield the burners and direct the gaseous medium circulatedby the fan 3 into the throat where the circulating gaseous medium mixesthoroughly with the combustion gases from each burner.

It will be appreciated that the pressure reducing throat is shaped as aventuri or orifice tube to cause a sharp rise in the velocity of thecirculating medium which together with an associated drop in the staticpressure within the throat enables the combustion products to enter theside ducts 5 without down draughts efi'ecting the burner or burnerssituated below the deflector plate 12.

The oven is provided with a vent or flue (not shown) connecting with theextract duct 7 at a point where the internal pressure is only slightlypositive in relation to atmospheric pressure, such that naturalaspiration prevents a build up of excess combustion products within theoven.

During comparative tests it was shown that this form of direct firedforced convection oven provides a considerable advantage in bothefficiency and thermal response times over the conventional andpreviously known forms of oven.

I claim:

1. A forced convection oven comprising an openable chamber defining acooking zone; fan means located in a compartment positioned below thecooking zone; inlet and outlet passageways between said compartment andthe cooking zone for circulating a gaseous medium through said zone; gasfuel burners positioned at each side of the oven for heating the gaseousmedium; said burners including ports arranged to fire directly upwardsinto the inlet passageways leading to the oven cooking zone; a pressurereducing throat within each inlet passageway and a deflector plate ineach inlet passageway for shielding the burners and directing thegaseous medium circulated by the fan into the throat so that thecirculating gaseous medium mixes with the combustion gases from eachburner before passing into the cooking zone.

2. A forced convection oven according to claim 1 wherein the gaseouscirculating medium comprises a mixture of air and combustion productsfrom the fuel burner.

3. A forced convection oven according to claim 2 wherein the openablechamber includes top, bottom, back and side walls, said side wallsincluding apertured panels therein and said back wall including anapertured panel therein, said oven further comprising means fordirecting the circulating medium into the cooking zone through theapertured panels in the side walls of the chamber so that, in operation,the medium flows substantially horizontally across the cooking zone andexits through the apertured panel in the back wall of the chamber.

t i l i

1. A forced convection oven comprising an openable chamber defining acooking zone; fan means located in a compartment positioned below thecooking zone; inlet and outlet passageways between said compartment andthe cooking zone for circulating a gaseous medium through said zone; gasfuel burners positioned at each side of the oven for heating the gaseousmedium; said burners including ports arranged to fire directly upwardsinto the inlet passageways leading to the oven cooking zone; a pressurereducing throat within each inlet passageway and a deflector plate ineach inlet passageway for shielding the burners and directing thegaseous medium circulated by the fan into the throat so that thecirculating gaseous medium mixes with the combustion gases from eachburner before passing into the cooking zone.
 2. A forced convection ovenaccording to claim 1 wherein the gaseous circulating medium comprises amixture of air and combustion products from the fuel burner.
 3. A forcedconvection oven according to claim 2 wherein the openable chamberincludes top, bottom, back and side walls, said side walls includingapertured panels therein and said back wall including an apertured paneltherein, said oven further comprising means for directing thecirculating medium into the cooking zone through the apertured panels inthe side walls of the chamber so that, in operation, the medium flowssubstantially horizontally across the cooking zone and exits through theapertured panel in the back wall of the chamber.